The immature nervous systems of animals and infants are exceptionally malleable. Brief periods of inappropriate sensory input during critical time windows of development can lead to permanent alterations in sensory perception. The effects of invasive and surgical experiences during infancy on the development of nociception have been surprisingly neglected. Our lack of understanding about the effects of childhood pain is underscored by the frequency with which human infants encounter pain during childhood, commonly arising from invasive procedures, surgery and trauma. Based on previous research and our current appreciation of how malleable even the adult nociceptive system is, it would be anticipated that painful experiences in young animals would have a permanent effect on adult pain sensitivity. The goal of these experiments is to determine how minor inflammatory injury in newborn rat pups permanently influences their mechanical and thermal sensitivity as adults, to identify the critical window of maximum susceptibility, and to begin to characterize the neural mechanisms that underlie altered pain sensitivity. The results of our studies are likely to impact our basic understanding of pain development and influence the clinical management of pain in infants.